Learn is a Computer-Based Teaching tool that gives basic training in using UNIX and Linux. It was written in the nineteen seventies at AT&T Bell Laboratories by Mike Lesk with some contributions from Brian Kernighan.
This version of the tool runs under Docker, which allows it to to run on a Windows system makes it easier to install on all systems. Docker can run on a Windows PC, a Mac, a cloud server or whatever. (I don't think it will run on a phone or a tablet.)
Learn teaches basic UNIX commands. It does so by driving you through a series of lessons each of which involves using commands to achieve some goal, such as creating a file with a specified contents. When you announce that you have finished the lesson, the software checks the result, marks the lesson and moves on to the next one.
Although the result looks a little antiquated, learn has proved to be extremely valuable because it works by getting you to use real UNIX commands on a real UNIX system.
Whichever system you use to run the learn tool, it needs to run git and docker. The installation process for those is different on each system. Once you've installed them, the process of building and running the learn tool itself is the same everywhere.
Docker runs under Windows 11 Home, recent versions of Windows 10 Home and under Windows Pro. To install it on Windows Home systems you also need to install the Windows Subsystem for Linux version 2 (WSL2).
A Digital Ocean Droplet or an Amazon EC2 instance both provide a cloud server on which you can run Docker and therefore the learn tool. You need to control a cloud server from a local machine such as a laptop computer. If that's running Windows, you need to install git bash on it as shown below.
Once you've installed Docker, you may wish to create an account on the docker hub, either using the docker app that's installed on your desktop (on Windows and a Mac) or via this web page. (You don't need to do that if you just want to run the learn software.)
To install Docker under Windows Home you first need to install the Windows Subsystem for Linux version 2 (WSL2) as described here. That involves running a DOS command window in admin mode: type "cmd" into the search box at the bottom of the screen, right click on the black icon that appears (marked "Command Prompt app") and choose "run as administrator".
That starts the command window. Select it, type
wsl --install
into it (that's wsl space hyphen hyphen install) and press the enter key to run the command.
If you're using a MAC you also need to know how to start a command window. That's described here
If docker is installed but not active (started) this command will start it:
sudo systemctl start docker
Under windows you need two command windows, the DOS command window that you used earlier to install WSL2, plus a git bash window.
In your command window, you see a prompt of some sort. Type a command and press the Enter key. The command runs. When it finishes, you get another prompt.
Run the commands one by one. Wait for each to finish before running the next.
Run this commands in your git bash window:
git clone https://github.com/goblimey/learn-unix
That creates a directory called learn-unix containing a copy of this repository.
In your DOS command window, change to that directory and build the docker image like so:
cd learn-unix
docker build -t learnunix .
(Note the "." at the end of the line.)
That last command will take a few minutes. It will produce output showing what it's doing. If all goes well, the last two lines should be something like:
=> => naming to docker.io/library/learnunix
What's Next?
View summary of image vulnerabilities and recommendation -> docker scout quickview
The first of those lines means that docker has built an image called learnunix
The second line suggests that you run docker scout. See later for more about that.
Once you've installed git and docker, you need to start a command window and run these commands:
git clone https://github.com/goblimey/learn-unix
cd learn-unix
docker build -t learnunix .
(Note the "." at the end of the line.)
That last command will take a few minutes. It will produce output showing what it's doing. If all goes well, the last two lines should be something like:
Successfully built 68b1841290ef
Successfully tagged learnunix:latest
The first of those lines means that docker has built an image with ID 68b1841290ef. You should only have to build the image once. If you run the build command again, you will get another image with a different ID.
The second line says that the image is tagged with the name "learnunix". You can refer to it by this name rather than the image name.
On any system, run the Docker image in a command window like so:
docker run -it --entrypoint=/bin/bash learnunix
(Under Windows, use a DOS command window to do that.)
That starts the image running within a container and produces a prompt something like this:
learner@79c33cdc14ac:/learn$
The docker session is running a version of Linux within whatever operating system your computer uses. You are logged into it as a user called "learner". The system is prompting for a command. To run the learn software, run this command:
learn files
and you will see this:
If you were in the middle of this subject
and want to start where you left off, type
the last lesson number the computer printed.
To start at the beginning, just hit return.
Press the Enter key and the first lesson will begin.
You can leave the command window running learn and do the lessons at your own speed.
Learn offers a number of courses, the most useful being Files and More Files. With good progress, it should be possible to get through both of those in one day, but it would probably be better done in a series of short sessions.
The learn software was aimed at an American audience, specifically colleagues at Bell labs in the nineteen seventies. Some of the lessons are biased to that culture. One requires a knowledge of baseball stars of the day. Being a Brit, I didn't have a clue what the answer was when I used learn back in the 1980s. I suspect that many Americans would have difficulty answering that one today. Use Google to find the answer or skip the question - nobody's watching you.
Another lesson asks about "an unsuccessful English king". The answer is George the Third, who was King when England lost the American colony. That may make sense to an American, but over here in the UK we remember George the Third for being mad, not unsuccessful. In other countries, people probably don't remember him at all, so that question would cause problems for some people.
A more serious problem with learn is that some lessons depend on material created in an earlier lesson and for various reasons, that may not have run. So occasionally learn might produce an impossible task. For example, it may ask you to find a file that's not been set up.
If you can't make sense of a lesson, skip it and move on to the next one.
If you want to pause and come back later, note the number of the last lesson you completed and shut the learn system down. To do that, hold down the CTRL key and type a single d (no Enter key needed). The learn command exits and you can type more commands into your your command window. If you type CTRL and d again you will exit from the container, it will die and you will be back in your command window on the host machine. If you carry on typing commands they run on the host machine.
Learn expects that various commands are available in the environment you are using: ls, cat, date, spell and so on. They should all be present in the docker image.
One of the most important commands that learn covers is man, the online manual. Knowing about man allows you to learn about lots more commands.
When you end the docker session, all the files that you created in it are tidied away. Unfortunately, learn also forgets how far you got. That's why you need to keep a note of your last lesson number. When learn starts, it invites you to give it a lesson number and continues from that point.
Once you've finished the Files course, do the More Files course.
It will take a few hours to do both courses. Do them at your own speed. If you don't end the docker session tidily by typing ctrl/d twice it will continue to run in the background, using up computer memory. You can end the session forcibly if you know its container ID. To find that out, start another command window and do this:
sudo docker ps
That produces a list of running docker containers, something like:
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
a5666adfd5d5 68b1841290ef "/bin/sh -c /usr/loc…" 2 minutes ago Up 2 minutes 2101/tcp happy_bassi
So in this example, docker is running image 68b1841290ef in container ID a5666adfd5d5. Stop that container like so, using its container ID:
docker stop a5666adfd5d5,
If you build an image under Windows, Docker invites you to examine it using something called Docker Scout.
Docker Scout is (in 2023) a new tool, currently on early access and free. See here to install it.
To use Docker Scout you must create a docker hub account. To use the scout from the command window, log into the hub:
docker login
then run the scout over your image:
docker scout quickview learnunix
✓ Image stored for indexing
✓ Indexed 319 packages
Your image learnunix │ 0C 0H 3M 44L 2?
Base image debian:12 │ 0C 0H 0M 17L
Updated base image debian:stable-slim │ 0C 0H 0M 17L
│
What's Next?
Learn more about vulnerabilities → docker scout cves learnunix
Learn more about base image update recommendations → docker scout recommendations learnunix
The second command "docker scout recommendations" suggests a few changes that will make the image a little smaller.
The first command "docker scout cves" runs a vulnerability search. It rummages through the version of Linux that you installed in the container (Debian Bookwork in this example) and all the packages that are installed, listing all of the vulnerabilities that have been reported. The report is very long. Here's the beginning:
docker scout cves learnunix
✓ SBOM of image already cached, 319 packages indexed
✗ Detected 23 vulnerable packages with a total of 48 vulnerabilities
## Overview
│ Analyzed Image
────────────────────┼─────────────────────────────────────
Image reference │ learnunix:latest
│ d8c2e3ed40b5
platform │ linux/amd64
vulnerabilities │ 0C 0H 3M 44L 2?
size │ 238 MB
packages │ 319
## Packages and Vulnerabilities
0C 0H 3M 0L linux 6.1.38-2
pkg:deb/debian/linux@6.1.38-2?os_distro=bookworm&os_name=debian&os_version=12
✗ MEDIUM CVE-2020-15802
https://scout.docker.com/v/CVE-2020-15802
Affected range : >=6.1.15-1
Fixed version : not fixed
✗ MEDIUM CVE-2022-38096
https://scout.docker.com/v/CVE-2022-38096
Affected range : >=6.1.15-1
Fixed version : not fixed
✗ MEDIUM CVE-2020-26555
https://scout.docker.com/v/CVE-2020-26555
Affected range : >=6.1.15-1
Fixed version : not fixed
Learn offers other courses, apart from files and more files, but the software that they teach about is of limited use to most users these days.
The Editor course covers regular expressions, which are useful, but the editor it describes is an ancient command-driven tool. You will probably learn more by typing "regular expressions" into Google.
The first lesson in the Macros course begins
"WARNING: This course was written for UNIX in 1979, not 1999, and has not yet been updated. Some details may be way out of date!"
Years later, that's not a good sign. Actually the macros involved could be useful, but only to people who wish to create and update UNIX man pages.
The Eqn course covers a typesetting tool that is still used, but the subject is somewhat of a niche.
If you use Microsoft Windows you need to install git bash to install the learn tool. Actually the real purpose of git bash is to add a UNIX-style command line interface to your Windows machine. Once you've complete the lessons and typed CTRL and d to come out of the Docker image, you will find that the commands that you've learned now work on your Windows system if you run them in the git bash window - "ls" lists the files in your current directory, and so on.
The most obvious command that's missing is "learn". You need to run the Docker container to get that.
Docker is free for personal use, but a large company may need to buy a licence to use it - see the Docker website.
Now that you have Docker installed, there's a huge amount of useful software out there that you can run for free. The Docker Hub contains thousands of ready-made Dockerfiles that you can use. Each one downloads and builds a piece of free software.
To build and install the learn software, Docker does this:
./configure
make install
That's a very common recipe for building free software. So if what you want is available but not already on the Docker Hub, you can download it, create your own Dockerfile to build it, then run it on a Windows PC, a Mac, a Raspberry Pi, an Amazon AWS server or pretty much anywhere. For example, see my reworked NTRIP caster here. Never mind what one of those is, the point is that the original is built and installed in the same way as the learn software, so the Dockerfiles for the two projects are very similar.
The learn software was originally included in version 7 UNIX which was released in 1978. I and many others used it in the eighties to learn the basics of UNIX. Since then I've made my living using those skills.
The software and the lessons were not reworked as UNIX developed and they became increasingly out of date. Versions of UNIX were released that didn't contain the learn software and it was largely forgotten. However, the material was preserved by the OpenBSD group.
The learn software was written in the C programming language. That language also evolved and eventually it became impossible even to build and run the learn software.
One reason for learn falling out of use is that through the nineteen nineties the emphasis shifted from command line interfaces to systems driven by windows and a mouse. Microsoft Windows became the desktop operating system of choice for most people, with the Apple Mac as a close second. UNIX systems were fitted with their own Windows interface so knowledge of the commands became less important.
In 2002 I reworked the learn source code so that it would compile and run, and bought it under the control of the standard GNU software configuration tools. That whole exercise took less than a week, which makes the original loss of the software a great pity.
At the time this work didn't gain traction, because of a chicken and egg problem. Learn is aimed at people who don't know much about UNIX, but they needed to know a certain amount to install and run it. Also, they needed access to a computer running UNIX. That could be done by installing Linux on an old Windows machine, but that involved knowing some UNIX commands ...
In 2019 I fixed that problem by reworking the learn system to run under Docker. At the time you could run Docker images on a Windows system but it was a bit fiddly. Now it's much easier, so you can finally use learn to teach yourself about UNIX and Linux before you invest in a real system.
That knowledge is useful because command line interfaces are back. We are all using Virtual Private Server (VPS) systems (AKA cloud computers). Virtual servers are very cheap and they can be set up and torn down to order using software such as Kubernetes, with the application software running under Docker. Linux is free so many virtual servers run it. Once they are running they are controlled by somebody connecting from a command window and running commands on them.
Apple's Mac range of computers have always run UNIX. It's heavily disguised behind a nice windows-style interface, but for some purposes you need to start a command window and type UNIX commands.
A more recent development is the emergence of very cheap single-board computers running Linux, such as the Raspberry Pi.
All this makes UNIX a mass-market product and a generation of IT specialists with a background in windows-driven environments have to get their heads around the UNIX command line interface. So the learn software has become valuable again.
The learn software and the courses are copyright AT&T, but a note in the source code gives permission for fairly free use. For the precise conditions, see the file LICENSE or any of the C source files.
The docker version is mainly intended for a machine running Microsoft Windows, as that's the most common environment available. Without docker, you would have serious difficulties getting learn to run there.
If you have your own Linux machines, you can clone the github repository and install learn permanently like so:
git clone https://github.com/goblimey/learn-unix
cd learn-unix/learn
./configure
make
sudo make install
See the INSTALL file in the learn directory for more complex environments.
There are three programs, learn, lcount and learn.tee. Learn is the front end and the user only needs to find that.
The lessons are text files. They are stored in the lib directory which contains a directory for each course. Lesson 3.1a is in the file L3.1a and so on.
The directory man contains the manual entry in nroff (man) format. When running the docker image, type
man learn
before you run learn command to read the manual entry for it.
A paper by Lesk in volume 2 of the version 7 UNIX manual explains how to write new lessons. Now over forty years old, the software looks clunky compared to modern CBT systems, but it runs under UNIX, it's implemented using UNIX, and when using it, the student is driven through using UNIX commands to achieve the results. This makes it a good medium for writing courses about UNIX.
(Having said that it looks clunky, Google's ultra-modern Go programming language is supported by a piece of training software that's only slightly more sophisticated.)
As Lesk explains in his origina paper, the main hurdle is to get the user started. To run learn, the student has to understand how to type commands. This is the first thing that learn teaches, if only she could figure out how to run it ...
I hope that you find the learn tool as valuable as I did all those years ago.
Simon Ritchie (goblimey.com)